Don’t waste your money on calcium supplements

Most supermarkets and pharmacies have shelves of supplements with health claims on their labels. Apparently, calcium and vitamin D supplements ‘‘help support’’ healthy bones and teeth. But what does that mean? If I think about what I ‘‘know’’ – it’s that calcium is good for bones and preventing fractures, especially as we age.

But how do I know that? And is it true? As a scientist, I could have read a study about it, but it’s more likely I’ve absorbed this information from product labels, advertisements, or talking with friends and family.

Also, what has calcium got to do with vitamin D, which our body makes from regular exposure to sunlight? One supplement company’s website says that vitamin D ‘‘assists the absorption and utilisation of calcium, which helps maintain healthy bone density’’.

So, here is what is known about calcium, vitamin D, and fractures, thanks to a recent study published in the Medical Journal of Australia by world experts Professor Ian Reid and Associate Professor Mark Bolland from the University of Auckland.

If you are a healthy adult getting daily exposure to the sun, you don’t need calcium or vitamin D supplements. Even if you are receiving treatment for osteoporosis, you don’t need to take extra calcium. In fact, calcium supplements can cause constipation, bloating, kidney stones, and possibly increase your risk of a heart attack. There’s four reasons not to take them.

Interestingly, frail nursing home residents were found to suffer fewer fractures if they took a low daily dose of vitamin D. At 400-800 units, that’s about half the daily dose recommended by the supplement makers. Higher doses were associated with more falls and fractures.

It looks like the link between fractures and vitamin D is related to a lack of sun exposure, so the experts suggest that other people who may also see some benefit from taking low-dose vitamin D are those with dark skin living at higher latitudes, and those who don’t get much sun exposure, perhaps because it is their custom to be veiled when outside.

I wonder what else I ‘‘know’’ to be true will turn out not to be.